693
AWUS01 KWNH 041813
FFGMPD
CAZ000-050600-

Mesoscale Precipitation Discussion 0019
NWS Weather Prediction Center College Park MD
111 PM EST Tue Feb 04 2025

Areas affected...Northern and Central California

Concerning...Heavy rainfall...Flash flooding possible

Valid 041800Z - 050600Z

Summary...Localized flash flooding is possible with additional
1-3"+ rainfall totals through 06z. Localities most likely to
realize isolated flash flooding from additional 3-5" totals are
along the northern foothills of the Sierras and the Santa Lucia
Range.

Discussion...Another round of moderate to heavy precipitation is
underway across portions of northern and central CA, driven by a
mid-level vort max leading an anomalous shortwave trough pivoting
into the Pacific Northwest (along with synoptic uplift provided by
upper-level divergence via the left exit region of a 130+ kt jet
streak). The 12z HREF indicates an additional 1-3"+ of QPF through
06z, with localities along the northern foothills of the Sierras
and the Santa Lucia Range most at risk of localized flash flooding
(with the highest chances for 0.5"+/hr rates and additional totals
of 3-5", per the 12z HREF 40-km neighborhood probabilities for
0.5" exceedance and ensemble agreement scale 0-100 km of 3.0"
exceedance, respectively). The HRRR has also been among some of
the wettest guidance, suggesting banded rainfall capable of
0.5-1.0"/hr rainfall rates extending into the lower elevations of
coastal regions (such as Santa Rosa and San Francisco). This seems
plausible, given the location of the surface boundary and the
uptick in low-level moisture flux convergence already underway per
SPC RAP analysis (along with the favorable synoptic environment
and total precipitable water values of 1.2"+ near the max moving
average, per OAK sounding climatology). Please consult local NWS
products for up-to-date information on flood hazards.

Churchill

...Please see www.wpc.ncep.noaa.gov for graphic product...

ATTN...WFO...EKA...HNX...LOX...MFR...MTR...STO...

ATTN...RFC...CNRFC...NWC...

LAT...LON   41232226 41182197 40922182 40512171 40212157
            39972125 39732092 39032065 38462016 37751965
            37391947 36991909 36571882 36321867 36041878
            36251903 36631941 36891963 37191985 37412019
            37602049 37522078 37372103 37082126 36702152
            36472146 36212119 35892084 35482062 35302078
            35362137 35772195 36402232 37162279 37802305
            38442338 38742315 39122321 39412339 39792365
            40072361 40452342 40812310 40972275 41122236